1. Field of the Invention
The present invention relates to an improvement of a magnetic head supporting mechanism in a interchangeable double side type flexible disc drive apparatus.
2. Description of the Prior Arts
It has been required to increase the capacity of memory and to reduce memory cost, and the demands made on memories have been remarkably increased. A flexible disc drive apparatus which is mainly used in a compact computer is a single side recording apparatus as well known.
In the past, only a single side of the flexible medium held in a flexible disc cartridge used as a memory medium has been used as a magnetic recording memory. In view of the requirement of improving cost performance, a double side type flexible disc cartridge using both surfaces of the medium as the memory surfaces and a double side type flexible disc drive apparatus has been commercialized. In the single side flexible disc cartridge, the medium is pushed from the back surface in contact with one magnetic head mounted on a carriage provided for moving and determining the position of the magnetic head in the radial direction, and the head is slided on the medium to perform write-in or read-out, and accordingly, the mechanism is relatively simple and quality control for the signals is easy.
In such an apparatus, the back surface of the medium is pushed by a pad made of a soft material to make contact between the medium and the head. On the other hand, in the double side type apparatus, the magnetic head is brought into contact with both surfaces of the flexible medium and accordingly, there are various manufacturing problems related to the stability of quality of signals and medium wear, in comparison with the single side apparatus.
In the single side apparatus, no medium wear is observed except in case of rough head surface, because the head surface is spherical and pressured by a soft pad from the back side.
However, in the double side apparatus, a pad can not be used, since the magnetic heads should be located on both surfaces of the medium. Accordingly, a wearing loss of the medium is produced by the magnetic heads on both sides of the medium. As the most severe problem, it is hard to prevent instant shock at the time of contacting of the medium by the magnetic heads. In order to prolong the life of the medium it has been considered to employ a method of maintaining a non-contacting condition during positioning of the magnetic head to a predetermined track or during non-operation of the apparatus, and contacting the medium at the time just before starting the read-out or the write-in. However, a peeling phenomenon is easily caused in the medium by repeating such contacts. In order to prevent such trouble, it is necessary to consider severe quality controls for the roundness value R of edges of the magnetic heads and a roughness of the surface of the magnetic head, a control of the contacting speed of the magnetic heads to the medium and a control of the angles of the magnetic head surfaces to the medium at the moment of contact. The double side type head supporting mechanism is one piece formed of a combination of a pressure arm and a cantilever spring supporting arm whereby the pressure force should be minimized in view of the life of the medium. Accordingly, remarkably soft structure is required to reduce the pressure force whereby the manufacturing process is quite difficult and the quality of signals is unstable.
The present status of the conventional double side type apparatus will be further described.
In FIGS. 1 and 2, the reference numeral (1) designates a spindle for giving a predetermined rotation to a magnetic memory medium in a flexible disc cartridge (2); (3) designates a cone on the spindle (1) which is fitted to a round hole (4) formed at the center of the medium (2); (5) designates a spindle cup for fitting the medium (2) to the spindle (1) by pushing the medium (2) from the upper position to the arrow direction A. The mechanism for supporting and rotating the spindle cup (5) is not shown since it is not important. The reference numeral (6) designates a body base for fitting and fixing the spindle (1). The magnetic memory medium (2) is rotated since the spindle (1) is rotated by a belt (not shown) on a pulley (30) formed in one piece with one end of the cone (3) and the belt is driven by a motor (not shown). A carriage body (7) is driven to change its position at the radial direction of the magnetic memory medium (2) by a lead screw or a belt, etc. (not shown). The driving source can be a known stepping motor (not shown). The stepping motor is firmly fixed on the body base (6) by L-shape fittings (not shown). An upper arm (8) is fixed on the carriage body (7) through a plate spring (9) with a screw (10). A lower arm (11) is fixed in the same manner. The plate spring (9) is formed in one piece by a mold inserting in an injection molding process with the upper arm (8) or the lower arm (11) as shown in the drawing. The reference numeral (28) designates each end of the upper or lower arm (8), (11); (29) designates an arm receiving surface formed on the carriage body. A projection (23) formed on each of the arms (8), (11) assists to suspend the support arm (14) to detach it from the surface of the magnetic memory medium (2). Each magnetic head assembly (12), (13) is firmly respectively fixed on the upper arm (8) and the lower arm (11) with each screw (25). The reference numeral (14) designates a head support arm attached by each screw (25). The reference numeral (20) designates a mounting base, which can be formed in one piece with arm (14) by a spot welding. A sliding type magnetic head (15) is firmly bonded on the end of the arm (14) with adhesive, etc. The reference numeral (21) designates a printed wiring flexible cable connected to the coil wound on the head (15) to lead out signals therefrom.
Referring to FIGS. 3, 4 and 5, the functions of the conventional magnetic head assemblies (12), (13) will be further illustrated.
The basic condition for using the magnetic memory medium (2) for a desired sliding life is to minimize the pressure force of the head (15) in an allowable range for maintaining signal output amplitude on the whole track without causing an amplitude modulation. In order to maintain a good following characteristic in its sliding operation to the flutter of the magnetic memory medium (2), a spring metal plate having a fine thin thickness is used as the support arm (14). Moreover, a pressure arm (16), is welded to the support arm (14) by a spot welding, to apply the pressure force on to the head (15). The end (17) of the pressure arm (16) is formed to push the projection (18) formed on the support arm (14).
The magnetic head assemblies (12), (13) are mechanically highly biased to the medium side when in a standby status by the pushing force applied to the projection (18) of the pressure spring (16), as in FIG. 5. In such structure, it is difficult to give an ideal design wherein the end (17) of the spring (16) is correctly located at the top of the projection (18) in its operation. The stress in a rolled flat plate is not uniform, the stress is released at the time of cutting whereby the support arm (14) cut from a flat thin plate can not be kept completely. Moreover, the flatness of the support arm is adversely effected by the heat given by the spot welding of the support arm (14) on the base (20). When these causes are piled up, the sliding surfaces of the heads (15) mounted in the carriage cannot be kept in parallel with the medium (2) in operation. The deviation of flatness of the support arm (14) causes also a deviation of line of force from being perpendicular to the surace of the medium (2) passing through a top of the projection for load (18) whereby the pressure force slanted with respect to the surface of the head (15) is imparted and accordingly, a slant gap is formed between the medium and the head to cause reproducing loss. Because of the deterioration of the flatness of the support arm (14) and the slant pressure force due to its uncertain dimension by its complex shape, the pressure spring (16) causes quick motion which deteriorates its output amplitude modulation excessively by the rotation of the medium (2). Moreover, as the magnetic head assemblies (12), (13) having such problems are located facing each other, combined adverse effects result whereby it is not easy to adjust them.
The undesirable amplitude modulation has been illustrated. As well known, such disc memory system has an important merit for interchangeability of the medium (2) so that the disc memory system has flourished. Thus, the conventional magnetic head assemblies (12), (13) have the disadvantage, that is, it is difficult to keep the positions of the magnetic heads (15), (15) for the magnetic gap within an allowable tolerance in their assembly because of the tendency for the support arms (14), (14) not to be flat and because of the cantilever structure of the support arms (14), (14). Thus, when they are mounted in the assembly, it is necessary to adjust the upper arm (8) and the lower arm (11) to the radial direction referring to the recorded standard medium in its operating test. Therefore, this further causes an output instability. Once the coincidence with line of force for the upper and lower magnetic head assemblies (12), (13) is found to provide stable amplitude, however the coincidence region is shifted by the adjustment of the magnetic gap position so that the undesirable condition is given.
On the other hand, the magnetic heads (15), (15) are departed from the surface of the medium while waiting so as to prolong the life of the medium in operation, as mentioned. At the moment for touching again the two facing magnetic heads come into collison with each other at each edge (19) of the magnetic head (15), through the medium (2) in the step of contacting operation. In order to improve the following characteristics of the magnetic head (15) to the radial direction and the circumferential direction, a fine thin plate is used as the support arm whereby it can not be balanced to the pressure spring (16), and the support arm (14) is bended as mentioned. Therefore, when the upper arm (8) and the lower arm (11) are turned to depart from the surface of the medium (2) around the fastening edges (26), (26) of the plate springs (9), (9) in the practical operation, the facing angles between the sliding surfaces of the magnetic heads (15), (15) and the surfaces of the medium (2) are held slanted with respect to each other and hard impacts are applied to both surfaces of the medium (2) upon subsequent touching by the edges (19), and accordingly, the damage is produced in an earlier period, to cause low industrial value. In order to overcome the disadvantage, the edges (19) should be formed to have the desired roundness R and is processed to form mirror surface. However, a hard brittle material is used as the slider, many processing steps are required and the processability is remarkably inferior for the control of the size of the predetermined R. Moreover, the facing angle between them is not uniform because of non-uniformity of the support arm (14) and the pressure spring (16) in their manufacture. Therefore, the value R for allowing such non-uniformity is large, and the flat area of the magnetic head slider (15) required for the stable sliding is reduced disadvantageously. The parallel condition of the surface of the magnetic head (15) and the surface of the medium (2) at the circumferential direction is often deviated in the rotation of the medium (2) by not only shape of the edge (19) but also distortion of the support arm (14), and the stick motion is caused by the contact of the forward edge of the magnetic head (15) in operation, so that the peeling of the magnetic coated membrane is disadvantageously caused in an earlier stage. Moreover, the rigidity of the flat cable (21) is comparable to the rigidity of the arm part (22), (22) of the support arm (14) whereby the following is also obstructed.
The disadvantages of the conventional head assemblies of double side type flexible magnetic disc drive apparatus have been discussed.
The supporting mechanism of the present invention will be illustrated hereunder. The features of the present invention are depending upon the following characteristics of the known plane gimbal spring which has round symmetrical shape with two-way compliance, the desired rigidity in the plane direction and the additional functions required for the sliding type disc memory.
The modified two-way plane springs having such gimbal function have been used as the supporting mechanisms for the floating type magnetic heads. However, as described above, they have been the floating type apparatus whereby the rigidity in the plane two-way has not been important because of a small coefficient of friction of air.
In accordance with the present invention, the gimbal spring is used in the contact type apparatus thereby requiring rigidity for withstanding the friction caused by the medium (2) and the vibration of the magnetic head (15) caused by the vertical flutter of the flexible medium which causes the running of the magnetic head on the slant surface of the medium and the rigidity for holding precisely the magnetic head position on the data track during operation.
At the same time, a quick following response of the magnetic heads to the vertical flutter of the medium (2) in its rotation is required.
The sliding type apparatus should be carefully designed in view of the above-mentioned functions which are not required for the floating type apparatus.
In the apparatus of the present invention, various functions are improved over the conventional double side type apparatus already mentioned.